Transcript Functions and Organs of Urinary System

URINARY SYSTEM & EXCRETION
URINARY SYSTEM & EXCRETION

Excretion
 The
removal of metabolic wastes from the body
 Kidneys are the primary organ of this process
FUNCTIONS OF THE URINARY SYSTEM

1. Excretion of Metabolic Wastes
 Removing
metabolic waste products, notably nitrogenous
waste from breakdown of amino acids (aa):

Urea


Breakdown of amino acids releases ammonia which is toxic to
cells)
Liver converts the ammonia to urea so it be safely transported in
the blood to the kidney where it is eliminated in urine
Creatinine
 Uric acid



if too much uric acid crystals can form in joints
This is known as gout
FUNCTIONS OF THE URINARY SYSTEM
FUNCTIONS OF THE URINARY SYSTEM

2. Maintenance of Water-Salt Balance
 Blood
volume is associated with salt balance in
body
 Salt
(NaCl) can cause water diffusion into blood
 ↑ salt = ↑ blood volume = ↑ blood pressure
FUNCTIONS OF THE URINARY SYSTEM

3. Maintenance of Acid-Base Balance
 Kidneys
regulate acid-base in blood
 Excretion of hydrogen ions and reabsorption of
bicarbonate to keep pH around 7.4
 Urine often has a pH of 6
FUNCTIONS OF THE URINARY SYSTEM

4. Secretion of Hormones
 Renin
 Leads
to secretion of aldosterone
 Reabsorption of sodium ions
 Erythropoetin
 Stimulates
 Activates
 Helps
tract.
red blood cell production
vitamin D from the skin
promote calcium absorption from the digestive
THE URINARY SYSTEM

Fig. 16.1
16-9
ORGANS OF THE URINARY SYSTEM

Kidneys
 Two
bean-shaped organs
 Located near lumbar region on either side of
vertebral column
 Has a depression called the
hilum where the Renal artery
Renal vein are located
ORGANS OF THE URINARY SYSTEM

Ureters
 Conduct
urine from the kidneys to the bladder
 Small, muscular tube 25cm long, 5 mm thick
ORGANS OF THE URINARY SYSTEM

Urinary Bladder
 Stores
urine until it is expelled from the body
 Located in the pelvic cavity
 3 openings (orifices):
2
for the ureters
 1 for urethera
ORGANS OF THE URINARY SYSTEM

Urinary Bladder con’t...
 Expandable
 Detrusor
Muscle – bladder wall
 Sphincter Muscles – surround bladder neck and urethra
ORGANS OF THE URINARY SYSTEM

While the bladder is filling:


the detrusor muscle is relaxed so the bladder wall
can expand and the sphincter muscles are
contracted to keep the urethra closed
When the bladder empties:

the detrusor muscle contracts to squeeze the urine
out, and the sphincter muscles relax so the urethra
can open up
http://www.aboutkidshealth.ca/en/howthebodyworks/kidneysandbladderoverview/bladderfillingandempt
ying/pages/default.aspx
ORGANS OF THE URINARY SYSTEM

Urethra
 Small
tube that extends from the urinary bladder to
an external opening
 females
4
cm long

Increases likelihood of urinary tract infection
 Not
connected to reproductive system
 Males
 20
cm long
 Common pathway for reproductive and urinary tracts
FEMALE & MALE URINARY SYSTEMS
URINATION

Micturition
 When
the bladder fills to 250ml
 Stretch
receptors in the bladder wall send sensory
impulse to the spinal cord
 Motor impulses from spinal cord send a signal the
bladder

 This
Bladder contraction and sphinter to relax
is called an involuntary reflex
 Present
in infants and young children
16-17
URINATION

In older children and adults the brain can
control this reflex and delay urination until a
suitable time
 Stretch
receptors in the bladder send a sensory
signal to micturition center in the pons
 If
not appropriate it will send an inhibitory signal to keep
the sphinter closed
 This
is called a voluntary response
 https://www.youtube.com/watch?v=US0vNoxsW-k